A radio frequency (RF) transmit pulse which energizes signals used in a magnetic resonance imaging (MRI) apparatus produces an inhomogeneous RF magnetic field (B1) due to influences such as attenuation in a living body. Since MRI signals thereby obtained are under the influence of the inhomogeneous magnetic field B1, partial inhomogeneity in brightness, namely shading, is caused in a final version of a magnetic resonance image (MR image).
In order to correct this shading, a technique of correcting an original MR image by estimating shading in an image obtained by subjecting the original MR image to background extraction and filtering, is known.
However, with this known technique, it is difficult to extract only inhomogeneity of brightness because the MR image has a high contrast. If a lesion is included in the image, the lesion may be regarded as shading and unnecessarily corrected. Furthermore, a high resolution increases a calculation cost. In the case in which an image with varying intensity of reception signals from a coil, for example an image of lumbar vertebrae, is corrected, a part that produces a weak reception signal is excessively corrected; as a result, viewability of the corrected image is significantly degraded.
Furthermore, in the case of obtaining a plurality of images, for example a T1 weighted image and a T2 weighted image, for a single patient, the above-described technique requires a longer processing time because shading needs to be estimated in all the obtained images.